AScribe NewswireJanuary 17, 2001 Massive floes of icenot catastrophic flooding may have
shaped some of the channels visible on Mars.A recent study has shown
that channels carved by moving ice on Antarctica bear a striking
resemblance to formations scientists have observed on the red planet.

Mars, the "red" planet as seen through the eyes of the Hubble
Space Telescope in 1997. Markings that appear to be channels on Mars
have long fascinated scientists.Photograph courtesy NASA

WASHINGTON Some channels visible on the surface of Mars may have
been gouged
by ice, rather than by catastrophic flooding, as is generally
believed. That is the view of Dr. Baerbel K. Lucchitta of the
U.S. Geological Survey in Flagstaff, Arizona, who compared the
Martian features with strikingly similar ones on the
Antarctic sea floor. Her findings are reported in the February 1
issue of Geophysical Research Letters, a publication of
the American Geophysical Union.

Outflow channels on Mars may be tens of kilometers (miles)
wide and hundreds of kilometers (miles) long, as are
some that Lucchitta studied in Antarctica. Ice flows in streams
within Antarctica's ice sheets before merging with ice
shelves in the surrounding ocean; the ones she studied flow from
West Antarctica into the Ross and Ronne Ice
Shelves. The martian channels arise suddenly from chaotic terrains
or fractures and terminate in the northern plains,
where there may once have been an ocean.

Both the Antarctic ice streams and some martian channels are
based below sea level, which on Mars is defined as
the average surface elevation of the hypothetical ancient northern
plains ocean. The Antarctic channels were mapped
using recently available sonar imagery.

Lucchitta demonstrates that martian channels, especially one
known as Kasei Valles, display similar characteristics
to those of Antarctic channels known to have been carved by ice
streams. She compares the Rutford Ice Stream at its
confluence with the Ronne Ice Shelf, where it diverges around an ice
rise, formed of more stable ice than the adjacent
flow, with Ares Vallis. The latter diverges around an island and
displays similar curved flow lines where it enters the
hypothetical ocean. The configuration of these two streams is
identical, she writes.

Lucchitta infers that Ares Vallis was filled by material that
had the characteristics of flowing ice that entered an ice
covered body of water. She believes that dust covered ice may
persist in Ares Vallis or that rocky material left an
expression of the flow forms after the ice evaporated. "The
observations strongly support the notion that an ocean
once existed in the northern plains of Mars," she says.

Another similarity between Antarctica and Mars noted in the
study is that some streams and channels rise in
altitude in the downstream direction. On Earth, uphill flow at the
base of ice is common, because the surface gradient
drives the ice, whereas water does not flow uphill for extended
distances.

There are differences between Antarctica and Mars regarding
the origin of ice in ice streams. On Earth, the
streams flow from ice sheets, while on Mars, it derived from fluids
erupting from below the surface. Also, on Earth, the
ice flows between ice walls, while on Mars it flowed between rock
walls, but the width to depth ratio on Mars is more
like that of ice streams than of mountain glaciers on Earth,
Lucchitta notes.

The study was funded by NASA's Planetary Geology and
Geophysics Program.

(c) 2001 AScribe Newswire

Editor's Note: More on Mars, including links to an online map of the
red planet, are available online in the February, 2001 issue of National
Geographic